Selecting a Test Method

ISO 877 [205] is an accepted standard for outdoor weathering which also describes the procedure for irradiation through window glass and for accelerated weathering by solar radiation with the aid of Fresnel mirrors. Further important standards include ISO 9845 [199], DIN EN 61725 [200] and ISO 9370 [206]. 

Investigations according to ISO 877 [207] require supports made from an inert material on which the fixtures for the specimens can be attached at a distance of at least 0.5 m from the floor surface. An irradiation gauge essentially consisting of a radiation collector and a current or tension integrator measures irradiation during exposure [86]. 

The results of such investigations depend to a large degree on local climate conditions at the location of weathering. The differences in radiation, temperature, and humidity that are determined by local climate and inherent to different exposure locations make it impossible to compare weathering resistances obtained in different locations. 

Experience has shown that two climate types are particularly important when testing weathering resistance  

These three ventilation variations may result in different resistance times even at the same specimen surface temperature, because the exhaustion of volatile components depends on the ventilation mode. 

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The specific analytical techniques discussed in this chapter and their main applications are detailed in Table 2. Sample homogeneity/heterogeneity may need to be addressed when selecting an analytical technique or designing a test method. 

E Nondestructive testing - leak test. Instructions for selection of a testing method 3/95... 

Sample shape and size are of considerable importance when selecting dynamic test methods for solid propellants. Preparation must take account of surface conditions and precise dimensions. Usually cast specimens retain a polymer-rich surface layer and should be avoided. Additionally, the sample dimensions should be large compared with the size of the largest solid particle inclusion in the propellant. 

The standard briefly covers the significance of hardness in terms of its relation with modulus, and the practical use of hardness tests. The hardness tests for rubber that are standardized by ISO are introduced and the distinction between dead load and durometer type instruments is explained to help with selection of a test method for particular circumstances. The effect of test piece, use of standard hardness blocks and comparison of hardness scales is also outlined. 

The above discussion has not covered all hardness test methods. However, the development of principal test methods for this parameter has been surveyed accurately as far as possible, chiefly with respect to minerals, in order to demonstrate both the difficulty of selecting a suitable method for testing a particular material (mineral or rock, natural or artificial), and the difficulty of interpretating the results given the wide variety of published test results. These contain errors arising from lack of knowledge of the precise type of measurement, for a material with stated strength properties. 

The most convenient and economic techniques of choice for the rapid analysis of starting materials and for the assessment of purity of a crude reaction product are t.l.c. and g.l.c. These techniques may also be used to monitor the progress of a reaction for which optimum conditions are uncertain, as may be the case when an established published procedure is used as the basis for carrying out other preparations of a similar nature. In these cases the reaction is monitored by the periodic removal from the reaction mixture of test portions for suitable chromatographic study. Clearly the chromatographic behaviour of starting materials and, if possible, expected products, needs to be established prior to the commencement of the reaction. For t.l.c. this would include solvent and thin layer selection, a detection method, and an appraisal of sensitivity of detection with respect to the concentration of components in the reaction medium. For g.l.c. preliminary experiments would be required to select a suitable column and the appropriate operating conditions. 

Document of material specifications and test methods. Verification of the specifications must be done to satisfy the design, and the test method must be validated where needed. Because the material is a critical safety factor, the selection of material for IOL should meet both the physicochemical and compatibility specifications described in ISO 11979-2 and 11797-3. The in-house (receiving) specifications of material should thus be documented. Where a test method is developed, the method must be validated. The equipment used for the test must be calibrated. 

Use a test method that has been validated to ensure correct identification and selective, accurate measurement of the analyte of interest Establish the bias associated with the mass transfer steps (digestion, extraction, evaporation, derivatisa-tion etc.) by measuring the recovery of spikes and by... 

A universal NDT method for evaluating bonded structures is not currently available. Generally, the selection of a test method is based on... 

Microbial Test Methods The selected microbial test methods determine specific sampling and analytical procedures. When the product has a potential antimicrobial effect and/or preservative, the spread technique on microbial test plates must be validated. In addition, the personnel performing the analytical techniques have to be qualified and adequately trained for this purpose [6],... 

The list below is a summary of test methods that are most likely to be required during the testing of most common dosage forms (tablets, capsules, and solutions). The list is by no means an exhaustive (since test methods to determine moisture content, pH, sterility, particulate matter, and microbial testing are not listed) and the selection of test methods depends on an evaluation of a dosage form and also on the phase of drug development. For each type of test, most common techniques utilized are listed in square brackets. As can be seen, HPLC can be employed for aU of the following test methods. 

A variety of natural and synthetic antioxidants are used in fat-containing foods in order to inhibit lipid oxidation with a wide range of efficiencies, depending on their properties, concentrations, and processing conditions. The need to measure antioxidant activity is well documented. Although numerous methods have been proposed for measurement of antioxidant activity, the essential features of any test are a suitable substrate, an oxidation initiator, and an appropriate measure of endpoint (9). Therefore, certain aspects should be taken into consideration when selecting a test for measuring antioxidant activity. These include the model food system used for... 

Second, there is an element of fashion or style attributed to a method either because of overzealous salesmanship, undue conservatism, or lack of knowledge of alternatives that often comes to play in the selection and review of a test method. The test should be able to stand alone as a means of answering specific questions about the effect of a xenobiotic. Tests that lack an adequate statistical or theoretical foundation should be avoided. Acquisition of data should not be an end unto itself. A well-designed toxicity evaluation should be comprised of toxicity tests that address particular questions which are the basis of the environmental concerns. 

The selection of appropriate methods for clinical laboratory assays is a vital part of rendering optimal patient care, and advances in patient care are frequently based upon the use of new or improved laboratory tests. Ascertainment of what is necessary clinically from a laboratory test is the first step in selecting a candidate method (Figure 14-1). Key parameters such as desired turnaround time and necessary clinical utflity for an assay can often be derived by discussions between laboratorians and clinicians. When introducing new... 

A convenient UV spectrophotometric method for in-process testing of the active ingredient is usually selected. A UV method can have a turnaround time of a few minutes compared with an HPLC method. Another advantage of the UV spectrophotometric method is that it does not require elaborate instrument and data acquisition systems and can be easily set up in a manufacturing environment. 

Jha AR, et al. 1979. A sensitive and selective spot test method for the detection of vanadium(V) in a water sample. Int J Environ Stud 14 235-236. 

Having decided what characteristics are necessary, it then remains to describe the product in terms of a specification. This entails selecting suitable test methods and setting appropriate limits. Many specifications in widespread use have evolved usually by the addition of extra clauses (rarely is a clause deleted). This has resulted in unnecessary restrictions that, in turn, result in increased cost of the products specified. 

There are several considerations when selecting a resampling method. The foremost is the sample size n. Additional considerations are on the proportion of the observations reserved for the test set and the number of times the error estimate is calculated. We address these considerations in the following sections and also refer the reader to supplementary discussions in McLachlan (1992) and Davison and Hinkley (1997). 

Flammability tests for textile goods do not involve any distinction between natural and synthetic materials. The selection of a test method is influenced rather by the field of application such as garments, household textiles (curtains, carpets, furniture covers, bedding), industrial protective clothing, etc. 

To select a forecasting method by retrospective testing on past demands. 

Appendix D lists methods of sampling and analysis which have been tested by NIOSH and OSHA for use with acrylonitrile. NIOSH and OSHA have validated modifications of NIOSH Method S-156 (See Appendix D) under laboratory conditions for concentrations below 1 ppm. The employer has the obligation of selecting a monitoring method which meets the accuracy and precision requirements of the standard under his unique field conditions. The standard requires that methods of monitoring must be accurate, to a 95-percent confidence level, to 35-percent for concentrations of AN at or above 2 ppm, and to 50-percent for concentrations below 2 ppm. In addition to the methods described in Appendix D, there... 

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